Electrical theories of the corona and zodiacal light, and their connection of some kind with the aurora borealis, have been put forth in many shapes, but so far as I have learned none afford any explanation of the _origin_ of the electrical disturbance. Without this they are like the vortices of Descartes, which explained the movements of the planets by supposing another kind of motion still more incomprehensible. Explanations which are more difficult to explain than the phenomena they propose to elucidate only obscure the light of true science, and stand as impedimente to the progress of sound philosophy. DR SIEMENS’ THEORY OF THE SUN. A paper was read on March 2, 1882, by Dr. C. W. Siemens at the Royal Society, and he published an article on “A New Theory of the Sun” in the April number of the _Nineteenth Century_. All who have read my essay on “The Fuel of the Sun” are surprised at the statement with which the magazine article opens, viz.: that this “may be termed a first attempt to open for the sun a debtor and creditor account, inasmuch as he has hitherto been regarded only as a great almoner pouring forth incessantly his boundless wealth of heat, without receiving any of it back.” Some of my friends suppose that Dr. Siemens has wilfully ignored the most important element of my theory, and have suggested indignation and protest on my part. I am quite satisfied, however, that they are mistaken. I see plainly enough that although Dr. Siemens quotes my book, he had not read it when he did so; that in stating that “Grove, Humboldt, Zoellner, and Mattieu Williams have boldly asserted the existence of a space filled with matter,” he derived this information from the paper of Dr. Sterry Hunt which he afterward quotes. This inference has been confirmed by subsequent correspondence with Dr. Siemens, who tells me that he saw the book some years since but _had not read it_. My contributions to the philosophy of solar physics would have been far more widely known and better appreciated had I followed the usual course of announcing firstly “a working hypothesis,” to warn others off the ground, then reading a preliminary paper, then another and another, and so on during ten or a dozen years, instead of publishing all at once an octavo volume of 240 pages, which has proved too formidable even to many of those who are specially interested in the subject. I am compelled to infer that this is the reason why so many of the speculations, which were physical heresies when expounded therein, have since become so generally adopted, without corresponding acknowledgment. This is not the place for specifying the particulars of such adoptions, but I may mention that in due time “An Appendix to the Fuel of the Sun,” including the whole history of the subject, will be published. The materials are all in hand, and only await arrangement. In the meantime I will briefly state some of the points of agreement and difference between Dr. Siemens and myself.